The 27-year-old defender has been linked with Celtic and Rangers, with the Glasgow rivals seeking to strengthen ahead of the new season.
No firm offers have been tabled for Shittu yet and Simpson told BBC Sport: "Danny is still with us and that´s the way it is staying."
Copyright (c) PA Sport 2008, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: https://www.givemesport.com/writeforgms